A cationic gold-fluorenyl complex with a dative Au ? C+ bond: synthesis, structure, and carbophilic reactivity

Aiming to study the interaction of gold with the highly Lewis acidic fluorenyl cation, we synthesised (o-[Ph2P(C6H4)Flu)AuCl(tht)][BF4] ([2][BF4]) and (o-Ph2P(C6H4)Flu)AuCl2 (3) (Flu = 9-fluorenyl) and found that the latter could be converted into [(o-Ph2P(C6H4)Flu)AuCl](+) ([4](+)) upon treatment with NaBArF24 (BArF24 = B(3,5-C6H3(CF3)(2))(4)). [4](+), which has been isolated as a chloride-bridged dimer, readily catalyses the cycloisomerisation of 2-allyl-2-(2-propynyl)malonate. Computational results show that [4](+) possesses a strong Au -> C+ bond and readily activates enynes.

Automated summary

In this study, two compounds were synthesized to investigate the interaction of gold with fluorenyl cation. Computational results showed that one of the compounds possesses a strong Au -> C+ bond and can effectively activate enyne compounds.